The methylation of cytosine residues in DNA is an important epigenetic alteration in eukaryotes. In humans and other mammals methylcytosine is found almost exclusively in cytosine-guanine (CpG) dinucleotides. DNA methylation plays an important role in gene regulation and changes in methylation patterns are involved in human cancers and certain human diseases. Among the earliest and most common genetic alterations observed in human malignancies is the aberrant methylation of CpG islands, particularly CpG islands located within the 5′ regulatory regions of genes, causing alterations in the expression of such genes. Consequently, there is great interest in using DNA methylation markers as diagnostic indicators for early detection, risk assessment, therapeutic evaluation, recurrence monitoring, and the like. There is also great scientific interest in DNA methylation for studying embryogenesis, cellular differentiation, transgene expression, transcriptional regulation, and maintenance methylation, among other things.
This disclosure relates to the detection of methylated DNA in a sample.